The family parameter label of the dimension. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2014 
Syntax
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| Visual Basic | 
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Remarks
 A dimension only can be labeled to a family parameter in a family document. Multi-segmented linear dimensions cannot be labeled. To unbind the family parameter, set this property to    a null reference (  Nothing  in Visual Basic)  . 
 Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentException | Thrown when the family parameter's ParameterType is not suitable for this dimension. | 
| Autodesk.Revit.Exceptions InvalidOperationException | Thrown when dimension can not be labeled. | 
| Autodesk.Revit.Exceptions InvalidOperationException | Thrown when failed to get the BuiltInParameter DIM_LABEL. |